A very handy tool for determinng the actual electricity cost to run the things around your house. I learned that my portable air conditioner costs about $1 per 24hrs to run. It takes a little bit of math to calculate but it's nice knowing what devices are costing you too much money to operate. I actually bought this device at Seattle Goodwill so I use it on lots of different items. Most devices only draw a fraction of the "rated load" that their stickers say.

Not as useful as I had hoped. I was hoping to figure out how much relatively low loads were pulling, like my TV when it is "off" but still pulling power, and my chargers for electronic devices. The lowest this reads is 0.1 watts, and the loads I was investigating were below that.

Easiest device to use, just plug in and plug electronics, etc. or multi-outlet extension cords into it. Push buttons to view electricity usage details at the moment and since you plugged whatever into it.
Tried two of the Kill-A-Watt monitors, and they provided solid proof that my roommate is wasting tons of power every day, so I just shove a page of all the useful data the monitor provides in his face whenever he attempts to blam me for the increasing electric bills (My power consumption = 28 % of the total electricity, and he uses 72% of it. Hmmm.
Seriously, I've cut my electrical consumption back to 22% thanks to the info the Kill-A-Watt tracks and displays in real time. My roommate says if I ever bring another KILL-A-WATT into our place again, I'll end up paying the library for the cost of one being lost...or try to get SPL to take a bunch of pieces of a Killed-And-Wrecked unit back; funny roommie, huh?